The invention relates to a method for reducing the surface tack of EPDM and related elastomers and to an EPDM elastomer having its surfaces coated with cellulose.
Uncured EPDM elastomers usually exhibit a sufficient degree of tack that if two surfaces of the uncured EPDM elastomer are brought into direct contact with each other, they will strongly adhere together. Thus, for example, if two sheets of uncured EPDM elastomer are brought into contact with each other, of if a sheet of uncured elastomer is wound up into a roll and the elastomer surfaces are permitted to remain in contact with each other for any significant period of time, it will be extremely difficult if not impossible to separate the sheets or unwind the roll. Such a problem is greatly magnified if the sheets or roll of elastomer are subjected to a curing procedure since the bond between the elastomer surfaces is greatly strengthened by curing.
In order to overcome the problem of EPDM elastomer surfaces adhering to each other during handling or after curing, it is necessary to apply a coating of an anti-sticking or lubricating agent to the elastomer surfaces. A number of such anti-sticking agents are known in the elastomer or polymer arts including talc, mica, starch and metal stearates. The most common anti-sticking agents used for elastomers are talc and mica. These materials effectively reduce the surface tension of the elastomer thereby reducing the tendency of the surfaces to stick together. Talc and mica strongly adhere to the elastomer surfaces but due to their lamellar structures permit the surfaces to slide past each other without sticking together.
As indicated, talc and mica are effective anti-sticking agents for EPDM elastomer surfaces. However, these materials exhibit a major disadvantage in certain EPDM elastomer applications. This disadvantage is particularly apparent in EPDM elastomers which are utilized for flat roofing applications. In such applications, it is usually necessary to splice two or more sheets of cured EPDM elastomer together with a contact adhesive in order to provide for complete coverage of the roof. However, talc and mica have been found to exert a negative effect on the peel adhesion of the splice or seam when a contact adhesive is used to splice the sheets of cured EPDM together. Thus, in order to achieve maximum lap splice strength it is necessary to completely remove the talc or mica from those portions of the elastomer surfaces which are to be spliced together. However, removal of the talc or mica is difficult and time consuming since these materials adhere strongly to the elastomer surfaces. As will be evident, the application of sheets of cured EPDM elastomer to flat roofs is a labor intensive operation. Accordingly, the necessity of completely removing the talc or mica is a significant disadvantage.
In view of the foregoing, the discovery of an anti-sticking agent which does not adversely affect the peel adhesion of EPDM splices, and therefore need not be removed or at least completely removed, would be a major achievement.